Extrusion of metal pipes and the like



Jan. 31, 1933. P. nuNsHEATl-l 1,895,881

EXTRUSION 0F METAL PIPES AND THE LIKE Filed June l27', 1951 In ue/zfar,

Patented Jan. 31, 1933 UNITED STATES PATENT oFFl'cEV PERCY DUNSHEATH, OF SIDCUIP, KENT, ENGLAND, VASSZIG'NOIB'LTO W. T. HENLEYS TELEf GRAPH WORKS COMPANY LIMITED, 0F LONDON, ENGLAND EXTIRUSION OF METAL PIPES AAND THE LIKE Application filed .Tune 27, 1931, Serial No. 547,370, and in Great Britain .Tuly 1, 1930.`

' This invention relates to the extrusion of metal pipes and the like, and to the application of lead or like sheaths to electric cables. The usual method of producing pipes or cable sheaths of lead and its alloys is to employ an hydraulic press, including a cylinder or container charged with molten lead which, as it cools, is forced forward in a semi-molten state through an annular space between al die and a point by the advancement ofa ram. In such apparatus various factors contribute to difliculty in maintaining uniformity of thickness of thesheathing, -whilst the very high pressures which have to be employed require correspondingly strong and heavy apparatus; further, owing to the necessity for refilling, the press must be stopped at intervals and the ram withdrawn. It has been proposed also to use, instead of a ram working in a cylinder, a screw-threaded member constituting a point holder or core rotatable within a cylindrical member constituting a casing formed with longitudinal ribs and/or grooves, means being provided for supply-` ing molten lead or lead alloy to-said screwthread by which it is extruded after solidication in the form of a tube or cable sheath.

An object of the present invention is to obviate the necessity for great strength of the body of the machine which is required, whichever of the above mentioned plants be employed.

According to the present invention the outer member or casing is screw-threaded' and the point holder or core is ribbed and/or grooved longitudinally whilst either may be rotated relatively to the other, and a suitable shaping die is secured to the adjacent end of said outer member or casing in such manner as to permit relative rotation therebetween and so that the tensile force generated in the apparatus and tending to separate the outer member of the casing and the shaping die, as a result of the compressive forces in the metal undervextrusion, are re-A sisted in the locality of said die without change in the general direction of the flow of the metal. For this purpose the outer member or casing may be formed externally, at or near its outlet end, with a iange which may be received in a groove o r space formed between the shaping die and a ring secured to, but spacedfrom, said die; for instance an L-section ring the internal ange of which underlies the external fiange on the outer member or casing, and if desired a ball bearing may be. interposed to take the thrust. l Preferably a small clearance is left between the two members and where a cable is to be sheathed by the apparatus the point holder forms a tube through which the cable is fed so that as it passes out through the die it is surrounded by the extruded metal.

Preferably, means are provided for 'cooling the outer of the two relatively rotatable concentric members beyond that part thereof where the molten metalenters it. In order to roduce a smooth exterior and interior sur ace on the mass of metal before it reaches the extruding die and to prevent the formation of fissures and folds in the metal the screw thread and the ribs and/or grooves may die away toward the outlet end, the former dying away before the latter as set out in the specification accompanying my copending application in Great yBritain for Letters Patent No. 334,315.

In order to prevent relative rotation between the metal and the walls of the passage through which it passes beyond the screw threaded outer member said walls are constituted by the ribbed and/or grooved inner member, or a part mounted thereon, on the one hand, and by the shaping die as an extension of the screw-threaded outer member, on the other hand, said shaping die'being stationary or rotary according as said screw Ithreaded outer member is rotary or-statio'nis still within the space between the relatively f rotatable concentric members where the screw thread on the outer member dies away, but through which the ribs and/or grooves on the inner member continue, and the third of which is a zone bounded, on the one hand, by the continuation of the inner member on which the ribs and/or grooves die away, and, on the other hand, by a smooth surface on the die which is stationary or rotary, according as said inner member is stationary or rotary.

The continuous movement of the metal in the narrow annular space between the relatively rotatable concentric members makes it an easy matter to obtain accurate temperature measurements of the metal at different points in the length of the passage, and accurately to control the temperature gradient in the metal, so that the metal which enters in the molten state can be made, by appropriate control of the cooling, to change from the liquid to the solid state as it travels forward.

Apparatus for `carrying the invention into effect is shown by the accompanying drawings in which Figure 1 is a sectional elevation of one form of apparatus and Figure 2 a section of a modified detail.

Figure 1 illustrates apparatus similar to that shown in my Patent No. 1,817,301, but of horizontal type.' A hollow point holder 1l is fixed centrallyin a horizontal position with respect to a' casing l2, rotatably mounted at its rear end on a spigot 13 carried by a main frame 14 and at its forward end on a ball thrust bearing, constituted by rings 15, 15 and balls 16, within. an L-section ring 17 connected by bolts 18 with a stationary member 19 carried by the frame 14. The spigot 13 is formed with channels 20 leading to the space between the members 11 and 12 from a chamber 21 into which molten lead -may be charged through an opening 22; the spigot 13 thus serves also as a support for the point holder 11. The casing 12 is formed with cooling gills 23 and has keyed thereto a worm wheel 24 meshing with a worm 25 rotatably mounted on the frame 14 and adapted to rotate said casing, the web of the worm wheel 24 being formed with cooling gills 26. At its rear end the point holder 11 is further hollowed to accommodate a vessel 27 of annular cross-section, connected with an inlet 28, and an outlet 29 for the circulation of a cooling medium such as oil to prevent overheating of the cable (not shown). The frame 14 is provided with an inlet 30 for the admission of a cooling medium for the gilled part of the casing 12, the open top of the frame 14 serving as an outlet. The point holder 11 is grooved and the casing 12 is formed with a screw thread as and for the purpose set forth in my before mentioned Patent No. 1,817,305.

vTo prevent any metal from escaping through the joint between the rotary casing 12 and the stationary member 19, (Figure 1),

the outlet end of the casing may be formed separately and of a softer metal. As shown in Figure 2 a tapered spigot 31 of e. g. bronze is attached rigidly to the end of the casing h and it is formed interiorly as a substitute for the screw threaded part which it replaces.

'Exteriorly, the spigot 31 is tapered and received in a conical recess in a die ,7'3 which constitutes a part of the stationary member y', the metal of the spigot 31 being cut away so that only a small area thereof at its outlet end contacts with the part ja against which it is forced by the pressure of the metal which is being extruded, thus forming a tight joint.

Another feature illustrated by Figure 2 is an increase inthe diameter of the point holder opposite the dying away of the thread, the object of this being to decrease the liability of the lead to form folds as the screw thread is eliminated.

I claim 1. Means for the continuous extrusion of metal pipes and the like, comprising two relatively rotatable concentric members the inner one of which forms a point holder or core and the other one of which forms a casing, said outer member being formed with a screw thread and said inner member with longitudinal ribs and/or grooves, said inner grooved point holder being fixed in a horizontal position and surrounded by the internally threaded cylindrical casing mounted so as to rotate on a, horizontal axis, while molten'metal is fed into one end of the space between said point holder and said casing, said molten metal feeding means being provided for supplying molten leador lead alloy to said screw thread by which it is extruded,`

after solidification, in the form of a tube or enable sheath, a suitable shaping die being secured to the adjacent end of said outer member or casing in such manner as to permit relative rotation therebetween and so that the tensible force generated in the apparatus .and tending to separate the outer member or casing and the shaping die, as a result of the compressive forces in the metal under extrusion, are resisted in the locality of .said die without change in the general direction of the flow of the metal.

2. Means for the continuous extrusion of metal pipes or the like as claimed in claim 1, in which the outlet end of the outr member or casing is formed separately as a tapered spigot of softer metal secured in the end of the casing -and formed interiorly as a substitute for the part which it replaces, the eX- teripr of said spigot being tapered so as to be received in a conical recess in a part f the stationary member, substantially as and for the purpose set forth.

3. Means for the continuous extrusion of metal pipes or the like as claimed in claim 1, wherein the point-holder increases in diameter opposite tothe dying away of the thread in the casing, substantially as set forth.

4. Means for the continuous extrusion of metalipes and the like, comprising two relative y rotatable concentric members, the inner one of which forms aointholder or core and the outer one of which forms a casing, said outer member being formed with a screw thread, and said inner member-with longitudinal ribs and/ or grooves, the internal screw thread on the casing, and the ribs and/or grooves on the point holder, dying away towards the outlet end and said oint holder bein fixed in a horizontal position, said casing eing mounted so as to rotate on a ,5 horizontal axis and means being provided for feeding molten metal into the space between said point holder and said casing, said molten metal feeding means being provided for supplying molten lead or lead alloy to -1 said screw thread by which it is extruded after solidiication in the form of a tube or` -cable sheath, a suitable shaping die being secured to the adjacent end of said outer member or casing 1n such manner as to ermit relative rotation therebetween an so v that the tensible Vforce generated inthe apparatus and tending to `separate the outer member or casing and the shaping die, as a result of the compressive forces in the metal under extrusion, are resisted in the locality of said die without change in the general direc-l tion of the flow of the metal, there bein three distinct zones in the apparatus, the rst of which is an impelling zone where there is little or no diminution in the depth of the screw thread or grooves, the second of which ,s still within the space between the relativelly rotatable concentric members where the screw thread on the outer member dies away, but through which the ribs and/or grooves on the inner member continue, and the third of which is a zone bounded, on the one hand,

-bv the continuation of the inner member on which the ribs and/or grooves die away, and,

y on the other hand, by a smooth surface on a member which is stationaryorl rotary, according as said `inner member is stationary or rotary. l

PERCY DUNSHEATH. 

